--- 1/draft-ietf-opsawg-tacacs-yang-03.txt 2020-05-08 20:13:04.054365956 -0700 +++ 2/draft-ietf-opsawg-tacacs-yang-04.txt 2020-05-08 20:13:04.074366220 -0700 @@ -1,19 +1,19 @@ Network Working Group G. Zheng Internet-Draft M. Wang Intended status: Standards Track B. Wu -Expires: October 21, 2020 Huawei - April 19, 2020 +Expires: November 9, 2020 Huawei + May 8, 2020 Yang data model for TACACS+ - draft-ietf-opsawg-tacacs-yang-03 + draft-ietf-opsawg-tacacs-yang-04 Abstract This document defines YANG modules that augment the System Management data model defined in the RFC 7317 with TACACS+ client model. The data model of Terminal Access Controller Access Control System Plus (TACACS+) client allows the configuration of TACACS+ servers for centralized Authentication, Authorization and Accounting. The YANG modules in this document conforms to the Network Management @@ -27,21 +27,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on October 21, 2020. + This Internet-Draft will expire on November 9, 2020. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -54,25 +54,25 @@ Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions used in this document . . . . . . . . . . . . . . 3 2.1. Tree Diagrams . . . . . . . . . . . . . . . . . . . . . . 3 3. Design of the Data Model . . . . . . . . . . . . . . . . . . 3 4. TACACS+ Client Module . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 12 - 8.2. Informative References . . . . . . . . . . . . . . . . . 13 - Appendix A. TACACS+ Authentication Configuration . . . . . . . . 14 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 13 + 8.2. Informative References . . . . . . . . . . . . . . . . . 14 + Appendix A. Example Tacacs+ Authentication Configuration . . . . 14 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 1. Introduction This document defines YANG modules that augment the System Management data model defined in the [RFC7317] with TACACS+ client model. TACACS+ provides Device Administration for routers, network access servers and other networked computing devices via one or more centralized servers which is defined in the TACACS+ Protocol. [I-D.ietf-opsawg-tacacs] @@ -140,26 +140,27 @@ This model is used to configure TACACS+ client on the device to support deployment scenarios with centralized authentication, authorization, and accounting servers. Authentication is used to validate a user's name and password, authorization allows the user to access and execute commands at various command levels assigned to the user and accounting keeps track of the activity of a user who has accessed the device. The ietf-system-tacacsplus module is intended to augment the - "/sys:system" path defined in the ietf-system module with - "tacacsplus" grouping. Therefore, a device can use local, Remote - Authentication Dial In User Service (RADIUS), or Terminal Access - Controller Access Control System Plus (TACACS+) to validate users who - attempt to access the router by several mechanisms, e.g. a command - line interface or a web-based user interface. + "/sys:system" path defined in the ietf-system module with the + contents of the"tacacsplus" grouping. Therefore, a device can use + local, Remote Authentication Dial In User Service (RADIUS), or + Terminal Access Controller Access Control System Plus (TACACS+) to + validate users who attempt to access the router by several + mechanisms, e.g. a command line interface or a web-based user + interface. The "server" list is directly under the "tacacsplus" container, which holds a list of TACACS+ servers and uses server-type to distinguish between the three protocols. The list of servers is for redundancy. Most of the parameters in the "server" list are taken directly from the TACACS+ protocol [I-D.ietf-opsawg-tacacs], and some are derived from the various implementations by network equipment manufacturers. For example, when there are multiple interfaces connected to the TACACS+ client or server, the source address of outgoing TACACS+ @@ -173,21 +174,21 @@ include the amount of data a user has sent and/or received during a session. The data model for TACACS+ client has the following structure: module: ietf-system-tacacsplus augment /sys:system: +--rw tacacsplus {tacacsplus}? +--rw server* [name] +--rw name string - +--rw server-type? enumeration + +--rw server-type? tcsplus-server-type +--rw address inet:host +--rw port? inet:port-number +--rw shared-secret string +--rw (source-type)? | +--:(source-ip) | | +--rw source-ip? inet:ip-address | +--:(source-interface) | +--rw source-interface? if:interface-ref +--rw vrf-instance? | -> /ni:network-instances/network-instance/name @@ -199,21 +200,21 @@ +--ro connection-aborts? yang:counter64 +--ro connection-failures? yang:counter64 +--ro connection-timeouts? yang:counter64 +--ro messages-sent? yang:counter64 +--ro messages-received? yang:counter64 +--ro errors-received? yang:counter64 +--ro sessions? yang:counter64 4. TACACS+ Client Module - file "ietf-system-tacacsplus@2020-04-20.yang" + file "ietf-system-tacacsplus@2020-05-09.yang" module ietf-system-tacacsplus { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-system-tacacsplus"; prefix sys-tcsplus; import ietf-inet-types { prefix inet; reference "RFC 6991: Common YANG Data Types"; @@ -244,45 +245,66 @@ "RFC 8341: Network Configuration Access Control Model"; } organization "IETF Opsawg (Operations and Management Area Working Group)"; contact "WG Web: WG List: Editor: Bo Wu - : Guangying Zheng "; + Editor: Guangying Zheng "; description "This module provides configuration of TACACS+ client. Copyright (c) 2020 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; - revision 2020-04-20 { + revision 2020-05-09 { description "Initial revision."; reference "RFC XXXX: A Yang Data Model for TACACS+"; } + typedef tcsplus-server-type { + type bits { + bit authentication { + description + "When set, the server is an authentication server."; + } + bit authorization { + description + "When set, the server is an authorization server."; + } + bit accounting { + description + "When set, the server is an accounting server."; + } + } + description + "server-type can be set to authentication/authorization/accounting + or any combination of the three types. When all three types are + supported, all the three bits are set."; + } + feature tacacsplus { description "Indicates that the device can be configured as a TACACS+ client."; reference "draft-ietf-opsawg-tacacs-18: The TACACS+ Protocol"; } identity tacacsplus { base sys:authentication-method; @@ -338,97 +361,90 @@ "Number of messages received by the server"; } leaf errors-received { type yang:counter64; description "Number of error messages received from the server"; } leaf sessions { type yang:counter64; description - "Total Number of sessions. A single-connection tacacs+ - connection may be >1 sessions."; + "Number of TACACS+ sessions completed with the server. + If the Single Connection Mode was NOT enabled, the number of + sessions is the same as the number of 'connection-closes'. + If the Mode was enabled, a single TCP connection may contain + multiple TACACS+ sessions."; } } } grouping tacacsplus { description "Grouping for TACACS+ attributes"; container tacacsplus { if-feature "tacacsplus"; must "not(derived-from-or-self(../sys:authentication" + "/sys:user-authentication-order, 'tacacsplus')) or server" { - error-message "When 'tacacsplus' is used as a sysytem" + error-message "When 'tacacsplus' is used as a system" + " authentication method, a TACACS+ server" + " must be configured."; description "When 'tacacsplus' is used as an authentication method, a TACACS+ server must be configured."; } description "Container for TACACS+ configurations and operations."; list server { key "name"; ordered-by user; description "List of TACACS+ servers used by the device."; leaf name { type string; description "An arbitrary name for the TACACS+ server."; } leaf server-type { - type enumeration { - enum authentication { - description - "The server is an authentication server."; - } - enum authorization { - description - "The server is an authorization server."; - } - enum accounting { - description - "The server is an accounting server."; - } - enum all { - description - "The group of all types of TACACS+ servers."; - } - } + type tcsplus-server-type; description - "Server type: authentication/authorization/accounting/all."; + "Server type: authentication/authorization/accounting and + various combinations. + When all three types are supported, all the three bits + are set."; } leaf address { type inet:host; mandatory true; description "The address of the TACACS+ server."; } leaf port { type inet:port-number; default "49"; description "The port number of TACACS+ Server port."; } leaf shared-secret { - type string; + type string { + length "16..max"; + } mandatory true; nacm:default-deny-all; description "The shared secret, which is known to both the TACACS+ client and server. TACACS+ server administrators - should configure secret keys of minimum - 16 characters length."; + should configure shared secret of minimum 16 characters + length. + It is highly recommended that shared keys are at least 32 + characters long."; reference - "TACACS+ protocol:"; + "TACACS+ protocol"; } choice source-type { description "The source address type for outbound TACACS+ packets."; case source-ip { leaf source-ip { type inet:ip-address; description "Specifies source IP address for TACACS+ outbound packets."; @@ -471,23 +487,21 @@ response from each TACACS+ server before trying with a different server."; } uses statistics; } } } augment "/sys:system" { description - "Augment the system model with authorization and accounting - attributes - Augment the system model with the tacacsplus model"; + "Augment the system model with the tacacsplus model"; uses tacacsplus; } } 5. Security Considerations The YANG module defined in this document is designed to be accessed via network management protocols such as NETCONF [RFC6241] or @@ -499,21 +513,31 @@ The NETCONF access control model [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. There are a number of data nodes defined in this YANG module that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative - effect on network operations. + effect on network operations. These are the subtrees and data nodes + and their sensitivity/vulnerability: + + /system/tacacsplus/server: This list contains the objects used to + control the TACACS+ servers used by the device. Unauthorized + access to this list could cause a user management failure on the + device . + + /system/tacacsplus/server/shared-secret: This leaf controls the + key known to both the TACACS+ client and server. Unauthorized + access to this leaf could cause the device vulnerable to attacks. This document describes the use of TACACS+ for purposes of authentication, authorization and accounting, it is vulnerable to all of the threats that are present in TACACS+ applications. For a discussion of such threats, see Section 9 of the TACACS+ Protocol [I-D.ietf-opsawg-tacacs]. 6. IANA Considerations This document registers a URI in the IETF XML registry [RFC3688]. @@ -528,22 +552,22 @@ registry [RFC7950]. Name: ietf-system-tacacsplus Namespace: urn:ietf:params:xml:ns:yang: ietf-tacacsplus Prefix: sys-tcsplus Reference: RFC XXXX 7. Acknowledgments The authors wish to thank Alex Campbell, John Heasley, Ebben Aries, - Alan DeKok, Joe Clarke, and many others for their helpful comments - and suggestions. + Alan DeKok, Joe Clarke, Joe Clarke, Tom Petch, and many others for + their helpful comments and suggestions. 8. References 8.1. Normative References [I-D.ietf-opsawg-tacacs] Dahm, T., Ota, A., dcmgash@cisco.com, d., Carrel, D., and L. Grant, "The TACACS+ Protocol", draft-ietf-opsawg- tacacs-18 (work in progress), March 2020. @@ -598,36 +622,45 @@ [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . 8.2. Informative References [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . -Appendix A. TACACS+ Authentication Configuration - - The system management model defines two authentication configuration - options, "local-users" and "radius", and use "user-authentication- - order" to control the authentication methods. As defined in - [RFC7317], the current system authentication methods model is as - follows: +Appendix A. Example Tacacs+ Authentication Configuration - +--rw system - +--rw authentication - +--rw user-authentication-order* identityref - ... + The following shows an example where a tacacs+ authentication server + instance is configured. - This draft defines the "tacacsplus" extension and therefore needs to - be configured in the same way. The 'tacacsplus' identity is defined - to control whether or not TACACS+ authentication should be used. + { + "ietf-system:system": { + "authentication": { + "user-authentication-order": [tacacsplus, local-users] + } + "tacacsplus": { + "server": [ + { + "name": "tac_plus1", + "server-type": "authentication" + "address": "10.10.10.2", + "shared-secret": "QaEfThUkO1980100754609236h3TbE8n", + "source-ip": "10.10.10.12" + "single-connection": "false" + "timeout": "10" + } + ] + } + } + } Authors' Addresses Guangying Zheng Huawei 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: zhengguangying@huawei.com